Article 10mm AUTO The Cartridge, The Myth, The Legend

The 10mm Auto, it almost vanished into obscurity. The brainchild of Col. Jeff Cooper who set out to make a flatter shooting cartridge than his beloved .45 ACP. He wanted it to be able to push a 200 grain bullet to 1200 feet per second, and it was achieved by shorting a .30 Remington case, blowing out the walls so it would accept the bullet from the .38-40 Winchester, a .400" bullet. Basing a pistol off the CZ75 design, the Bren-Ten was born, but it came at a price. $500 was a lot of money in 1986 and the company ended up filing for bankruptcy. Luckily Colt decided to pick it up in 1987 and started producing a 1911 called the "Delta Elite". This pistol is part of the reason we still know about the 10mm today. The other reason is probably because agent Dove's 9mm bullet stopped one inch shy of Platt's heart in the Miami-FBI shootout (see 1986 FBI Miami Shootout). Some speculate that Dove and Grogan might have survived if that bullet had pushed one inch farther.

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So the FBI decided they needed more powerful handguns. They adopted the 10mm Auto, in its full power form, it puts it square between a .357 Magnum and a .41 Magnum. They started using Smith & Wesson 1076 pistols. They were a variant of the S&W 1026, except the 1076 had a 4.25" barrel and a frame mounted decocker vs the slide mounted decocker on the 1026.They also contracted H&K to build MP5's in 10mm for their "SWAT" style teams, and those are still in use today.

After agents started using these new handguns, qualification scores dropped considerably compared to the old 9x19 pistols. The recoil of the full bore 10mm proved to be too much for most agents. They began testing with "Reduced Recoil" ammo to try to improve scores and make the guns more manageable. The request for the new ammunition was passed to Federal Cartridge. This is the loads that became known as "10mm Lite", and several makers still make loads in power range. Of course when they started using lighter loads, the pistols became reliability disabled. Smith & Wesson's solution was to take the case from 25mm to 22mm and they were still able to copy the performance of the FBI Lite loads. This new version of the cartridge became known as the .40 S&W, and it also fit in 9x19 size pistols, which let shooters with small hands handle them better, and qualification scores improved again. Law
enforcement agencies all around the US adopted this new cartridge and it has enjoyed great success.

The 10mm Auto has always been around in guns like the Glock 20, Glock 29, Colt Delta Elite and some more along the way. A lot of self defense handgun owners only ever considered the 10mm for a woods defense gun, when hiking or hunting. Everyone feared if used for self defense against human targets that over penetration would be a severe problem, hurting bystanders and going through walls. It wasn’t until ballistic gel testing started to become popular that people learned the faster you pushed a hollow point bullet the LESS it penetrated. It actually takes well-constructed hollow points to handle the full power of the 10mm Auto. Bullets like the bonded Speer Gold Dot and the Hornady XTP. This turns the big 10 into a great self-defense firearm. Underwood Ammo, Buffalo Bore, & Double Tap Ammo are great places to get ammo tuned to get full potential out of the 10mm, 180 grain bullets at 1300 feet per second, and 200 grainers at 1250. They also sell 200-220 grain hardcast ammo for woods defense against 4 legged critters out to put you down. Plus here in 2016, the 10 seems to be making a comeback. You've got the Glock 20/29/40 and the Delta Elite like before, but now Sig Sauer is making a P220 in 10mm, Dan Wesson is in the game, Kimber, Nighthawk, STI, and Tangfolio too.

This isnt just about the 10mm's accomplishments as the cartridge itself. Let’s not forget it's children that it has given us and their success as well. The .40 S&W, probably still the most commonly used law enforcement cartridge. The .357 SIG, pushing a 125 grain bullet at 1350 1450 fps (depending on ammo used), and quickly nipping at the .40 S&W's heels, as tons of LE departments are adopting it. The 9x25 Dillion, this one seems to be just for fun, because there aren’t any .355" bullets that will hold up to its speed. 124 grain bullet at 1700
fps.

So when you are in a gun shop glancing around and see a 10mm pistol, don’t just think of a cartridge that almost disappeared into firearm history. Think of how amazing the round is and maybe give it a chance, or at least be thankful for its offspring that citizens and LEO's carry every day. The 10mm Auto is here to stay, and there are those of us who like it, and love to feel that recoil of this amazing cartridge. For the hand loader it can be anything from a .40 S&W to something right up at the .41 Magnum. It's probably one of the most versatile cartridges in existence, just give it a chance.

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Recent User Reviews

Love my G20 with 5.3" ported Storm lake barrel loaded hot with 180 grain hard cast. 15+1 rounds of hog stopping power. I find the recoil of the 10mm is very manageable and my 12 year old son shoots the pistol well. I chamber only one round and drop the mag. of course before letting him shoot. Where else can you get so much firepower in a semi auto? Try the 10mm, its an awesome woods gun.

Good article. I'm glad to see the 10mm making something of a comeback. My first semi-auto pistol was a S&W 1006 that I got back in the early 90's. That was and still is a great pistol. Since S&W is no longer making parts for it, last year I got a G-20 to use as a woods and home defense gun. A G-20 with 15 in the mag and one in the tube offers a lot of firepower to deal with both 2 and 4 legged critters!

Once you get used to the 10mm with stout ammo, (I have a LOT of Sig Elite, 180gr @ 1250fps) everything else feels like a pu$$ycat! Also got some Buffalo Bore and Underwood, when I'm feeling froggy If that does not do it, I have an LWD longslide for my G21, it's a 460 Rowland Conversion.

I just got my first Glock, a G29. Can't wait to get to the range but that won't be for a couple more days.
I got the bug for 10mm when Colt came out with the Delta Elite in the late 80s, but ended up going with .44 Mag instead. Now, I'm finding I don't enjoy the big .44 as much as I did in my younger days, so finally gave in to that 10mm itch that's been nagging me for thirty years.

Alas, there is no mention of Dornaus and Dixon who put their reputations and fortunes on the line to bring the Bren Ten and the 10mm Auto into production. In particular, it was Mike Dixon who finalized the specifications for the 10mm Auto. Cooper took the glory but not any responsibility for making the new pistol and cartridge a reality. Here is a link to an article about the beginnings of the 10mm Auto:

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